1. Field of the Invention
The invention relates to a vehicle suspension in which the height of one or more axles is controlled with a height control valve which inflates one or more air springs mounted between the vehicle frame and the axle and, more specifically, to a vehicle suspension having a rotary height control valve. The height control valve can also be used to control the height of a vehicle cab relative to the vehicle frame when air springs support the cab.
2. Related Art
Pneumatic vehicle suspensions often have a leveling device for controlling the height of a vehicle frame relative to a vehicle axle. This leveling device, often called a height control valve, controls the amount of air within an air spring located between the frame and the axle. The height control valve typically controls the air pressure in the air spring in response to changes in the distance between the frame and the axle by selectively interconnecting the air spring with a supply of pressurized air or an exhaust port. The height control valve has its greatest use in maintaining a constant level of a vehicle chassis or frame relative to its axles in response to the loading and unloading of the vehicle, often referred to as the xe2x80x9cride heightxe2x80x9d of the vehicle.
FIG. 1 illustrates a typical prior art height control valve 10 mounted on a frame 12 of a vehicle by bolts 14. The valve 10 is adapted to supply air to an air spring 22 which is mounted between the frame 12 and an axle support 24, such as a trailing arm, so that the upward and downward movement of the frame 12 relative to the axle support 24 actuates the height control valve 10 to normally exhaust air from or deliver air to the air spring 22.
Air is typically supplied from a source of pressurized air such as a tank 26 by a supply tube 28 connected to an inlet port 30 of the height control valve 10. The air is delivered to the air spring 22 through a delivery tube 32, which is connected to a delivery port 34 of the height control valve 10. Air is exhausted from the air spring by an exhaust tube 36 connected to an exhaust port 40 and is vented to the atmosphere as shown in FIG. 1. An actuator arm 42 extends from the height control valve 10 and is connected to a linkage 44 extending between the axle support 24 and the vehicle frame 12. In operation, movements of the axle support 24 relative to the frame 12 pivot the actuator arm 42 through the linkage 44 to control the height control valve 10.
Height control valves for vehicles, though known for years, remain problematic. Problems include a large number of parts leading to high assembly and service costs. Seal wear presents a further problem with prior height control valves due to the repetitive motion intrinsic to the operation.
The invention relates to a trailing arm suspension comprising a frame bracket adapted to be mounted to a vehicle frame, a trailing arm pivotally mounted to the frame bracket, and an air spring mounted on the trailing arm and adapted to be mounted to the underside of the vehicle frame. A height control valve is adapted to be fluidly interconnected to a source of pressurized air and to the air spring and has an arm adapted to be connected to the trailing arm to control the flow of pressurized air to the air spring and the exhaust of pressurized air therefrom in response to pivotal movement of the trailing arm with respect to the vehicle frame.
According to the invention, the height control valve comprises a housing having a cylindrical bore, a supply port, an exhaust port and an air spring port each of which extends through the housing and fluidly communicates with the bore. A rotor is rotatably mounted in the bore and interconnected to the arm wherein pivotal movement of the arm rotates the rotor with respect to the housing between first, second and third rotational positions. A plurality of seals is located between the rotor and the bore defining a flow passage between the bore and the rotor wherein in the first rotational position, the flow passage isolates the air spring port from both the supply port and the exhaust port, in the second rotational position the flow passage interconnects the air spring port with the supply port, and in the third rotational position the flow passage interconnects the air spring port with the exhaust port.
The flow passage is preferably defined by a pair of circumferential seals. The rotor preferably has a longitudinal axis and the flow passage is inclined at an acute angle with respect to the longitudinal axis. The seals preferably comprise a circumferential seal located at each end of the rotor. The seals are preferably o-rings. The rotor of the height control valve can have a plurality of circumferential grooves, each of which receives an o-ring seal.
The seals can be configured so as to provide a dead band for the suspension, wherein small movements of the axle relative to the frame are attenuated. The configuration of the seals and the position of the ports can cooperate to define a characteristic flow rate of the valve.
Other objects, features, and advantages of the invention will be apparent from the ensuing description in conjunction with the accompanying drawings.